President Obama has ordered the U.S. military to withdraw 10,000 troops from Afghanistan by the end of the year and pull out another 23,000 by the summer of 2012, part of what he called "the beginning, but not the end, of our effort to wind down this war."

"After this initial reduction, our troops will continue coming home at a steady pace as Afghan security forces move into the lead," Obama said in a primetime address to the nation Wednesday night from the East Room of the White House. "By 2014, this process of transition will be complete, and the Afghan people will be responsible for their own security."

The president said his announcement was a fulfillment of a commitment he made in December 2009 when he authorized a surge of 30,000 U.S. forces into Afghanistan. At the time, he also promised to begin a drawdown in July 2011.

The withdrawal of 33,000 troops by next summer effectively brings home all the "surge" troops he deployed leaving roughly 70,000 behind.

Obama argued that the U.S. has made progress on many goals: disrupting and dismantling al Qaeda and inflicting "serious losses" on the Taliban.

"We have put al Qaeda on a path to defeat, and we will not relent until the job is done," he said.

The president said the U.S. goal in Afghanistan was not to "try to make Afghanistan a perfect place," but to ensure it will never be a safe haven for terrorists -- a goal that he stopped short from declaring achieved.

Still, in a nod to the war-weary public and his congressional critics, Obama said it is now "time to focus on national building here at home."

"Over the last decade, we have spent $1 trillion on war at a time of rising debt and hard economic times," he said. "Now, we must invest in America's greatest resource -- our people."

All told, the war in Afghanistan has cost taxpayers more than an estimated $443 billion, according to the Congressional Research Service, and the lives of at least 1,523 U.S. military service members.

According to the latest ABC News polling, 73 percent of Americans say the United States should withdraw a substantial number of U.S. combat forces from Afghanistan this summer. Yet far fewer, 43 percent, think that will happen.

Americans also question the long-term impact of America's presence in Afghanistan. Fifty-seven percent say the war has contributed to the long-term security of the United States. But far fewer, 25 percent, say it has contributed "a great deal," which is the kind of payback many want to see, given the war's steep price tag. The United States has spent roughly $112 billion in Afghanistan this year alone.

The pace and scope of Obama's withdrawal strategy has put him at odds with the recommendation of the military and some Republicans.

Sen. John McCain, a leading supporter of the war effort, said earlier this week he would be "very reluctant to reduce the surge troops capability" in Afghanistan and that they should remain for at least one more fighting season in order to "get this thing pretty much wrapped up."

Even Defense Secretary Robert Gates, who is set to retire at the end of the month, said earlier this week that he was concerned the gains in Afghanistan were "very fragile" and subject to reverse.

Tonight, however, Gates endorsed the president's strategy, saying it will work.

"Over the past 18 months, our troops have made tremendous progress degrading the capability of the Taliban while enhancing the Afghan security forces. It is critical that we continue to aggressively prosecute that strategy," he said. "I support the president's decision because it provides our commanders with enough resources, time and, perhaps most importantly, flexibility to bring the surge to a successful conclusion."

On the front lines, many U.S. service members contacted by ABC News said they remain determined towards the same goal.

"We're here to do one thing: We're here to win, and that's what we did, we won," said Sgt. Mendez of the No Slack Battalion, 101st Airborne Division, who did not want to give his first name. "It's going on a decade we've been fighting this war. ... I don't see us getting out of here anytime soon. But we are making a difference, we are taking it to the enemy now."